1. Field of the Invention
The present invention relates generally to fasteners, and more particularly is concerned with a device for continuously advancing fasteners in a magazine for a fastener driving device.
2. Description of the Prior Art
Fastening tools are used by industrial employees, construction workers, and even homeowners. Fastening tools provide an economical and efficient means for fastening parts and pieces together and are frequently utilized in a wide variety of industries. A representative example of such a device is shown and described in U.S. Pat. No. 2,983,922, which is assigned to the assignee of the present invention.
Generally, fasteners for such tools are carried within a magazine. The magazine may be an integral part of the tool, or may be separately mounted on the tool. Fasteners are fed forward within the magazine such that the forwardmost fastener is positioned beneath the driver such that it can be driven from the tool into a workpiece upon activation of the tool.
For continuous operation of a fastening tool, it is important to maintain a constant forward force on a row of fasteners so that the fasteners advance within the magazine as each one is driven. Such force causes the fasteners to advance so that the next fastener in line will be positioned properly after the previous fastener has been driven. In desk staplers and in many industrial tools, this force is often applied by a spring-biased member which slides behind a row of fasteners and causes the fasteners to advance as the first fastener in a row is ejected.
Oftentimes, automatic fastening devices, either pneumatically or electronically powered, are used in high volume, high speed production areas. An example of this is taught and described in U.S. Pat. No. 4,562,949. The apparatus shown in this patent uses a plurality of stapling tools for the purpose of constructing lattice automatically and continuously with a minimum of labor.
Devices such as that shown in U.S. Pat. No. 4,562,949 drive a large number of fasteners in a short period of time; thus, it is necessary to often replenish the supply of fasteners for the magazines of the stapling tools. If the tools use a spring-biased member to advance the fasteners in the magazine, it is a very time-consuming task to replenish the fastener supply, which task may greatly reduce the efficiency and speed that the device is designed to provide, especially if there is a large quantity of tools having magazines which hold a limited number of fasteners.
In some applications, devices have been designed to continuously supply fasteners to a fastener-driving tool. Examples of these types of devices are shown in U.S. Pat. Nos. 3,604,608 and 4,574,991. However, devices such as these are typically relatively complex, using pneumatic cylinders to load and position staples for use in fastener driving tools. The drawbacks of such devices include reliability problems (due to the complexity of the systems), and the cost.
Another device for storing and supplying a large number of fasteners to a fastener driving device without stopping to reload is shown and described in U.S. Pat. No. 3,189,220. The device taught therein has a storage section which accommodates a large number of staples in the form of sticks or strips of detachable joined fasteners. The strips of staples are discharged transversely from the storage section against a stop, and guide means are provided interconnecting the storage section and the stop with the staple feed track for receiving a strip of staples from the storage section and advancing strips onto the staple feed track. A continuously driven fastener advancing mechanism is provided for resiliently bringing the staples in the guide into and toward the discharge end of the feed track and also for advancing sticks of staples from the storage section in driving engagement along the guide.
While this device is much simpler than the aforementioned patents, it still employs a bevel gear assembly to drive both a friction staple driving apparatus and a belt driven staple advancing pulley assembly from a single continuously operating motor. The staple driving apparatus uses a spring as a lost motion connection between the bevel gear assembly and the staple driving wheel such that the wheel responds in an intermittent advancement to the continuous drive of the gear assembly, with the driving wheel slipping when the spring is stretched to its limit. The O-ring belt which frictionally engages the staples also slips as the continuously operating motor slightly overdrives the staple advancing mechanism. As a result, there is constant wearing of some of the parts of this device, which may cause feeding problems.
Another problem which can effect the operation of the device taught in U.S. Pat. No. 3,189,220 is caused by the breaking of the staple strips. Although the staples are fastened together by glue, tape, or some other adhesive, it is not uncommon for these strips to break apart while being handled. This could possibly cause a feed problem in this system.
Consequently, a need exists for improvements in devices for continuously supplying fasteners to a fastener tool. A device should be easy to install, simple to operate, inexpensive to manufacture, and need a minimum of maintenance. The device should advance fasteners into a magazine so that each fastener is properly aligned for ejection.